1. Technical Field
The present invention relates generally to digital image printing; and, more particularly, it relates to K replacement within digital image printing systems.
2. Related Art
Conventional printing systems that employ K replacement typically have at least four channels. These channels most often distribute cyan, yellow, and magenta ink on a printing medium. Examples of printing media include paper and film on which ink is placed to generate a substantially imperceptible reproduction of a plurality of image data. The combination of these three inks together, ideally, results in a substantially black color. However, various undesirable results occur when the three inks are placed simultaneously on the printing medium. Because the actual inks used in a printing system are not themselves spectrally pure, the combination of the three non-black inks generates a color that is often not truly black. Additionally, the printing of three ink pixels on top of one another often wets the paper and results degraded image reproduction. A fourth channel, a black channel typically referred to as a K channel, is used to overcome these problems associated such printing system. The K replacement method typically detects when all three of the inks are to be used to print in a given pixel.
Typically, an error diffusion method is performed to all the four channels of such a printing system. During the computational process, the K replacement is only performed when all of the channels are to print ink in a given pixel. Still, error diffusion processing is also often performed using the fourth channel, despite it being a residual ink channel. The use of four channels in conventional systems requires the dedication of increased processing resources than that which is required by the three channels themselves. The conventional method of performing error diffusion on all four of the channels is invariably cost prohibitive in some applications in that the cost budget simply cannot accommodate the addition of the processing resources required to perform the error diffusion on the fourth channel.
Further limitations and disadvantages of conventional and traditional systems will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings.
Various aspects of the present invention can be found in an image processing system that converts a plurality of image data into a form suitable for printing. The invention takes in the plurality of data into the image processing and operates on the plurality of data to convert it so that it may be displayed or reproduced on a printing medium. In certain embodiments of the invention, the printing medium is paper in which a printer deposits at least one of either ink, wax, or some other medium that leaves a visibly perceptible modification to the printing paper for viewing of the plurality of image data in a manner substantially similar to the actual and original representation of the plurality of image data.
In certain embodiments of the invention, the image processing system may be contained within a multi-functional peripheral. The multi-functional peripheral device is a peripheral device containing a plurality of internal devices wherein each of the devices operates either independently or cooperatively to process the plurality of image data.
In other embodiments, the invention includes a method that employs K replacement to a plurality of pixels that are generated using the image processing system. In certain embodiments, the image processing system detects whether or not ink is to be printed using all of the available print channels in the system. If ink is to be printed using a predetermined number of the channels, then the image printing system performs K replacement.
Additionally, error diffusion is applied to the predetermined number of the channels. In certain embodiments, the error diffusion utilizes a predetermined threshold mask to diffuse the error to pixels adjacent to the pixel. Alternatively, the predetermined threshold mask is used to diffuse the error to pixels that are not immediately adjacent to the pixel. In either embodiment, the error is diffused to pixels contained within the plurality of image data.
In certain embodiments, K replacement is performed only when the spectral content of a given pixel falls within a predetermined range of a spectrum. This spectrum may be a color spectrum wherein the spectrum varies across the entire visible spectrum in certain embodiments. In other embodiments, the spectrum is an intensity spectrum wherein the spectrum varies from a highest intensity to a lowest intensity. The characteristic of the pixel is intensity in certain embodiments of the invention. In other embodiments, it is a color component of the pixel.
Other aspects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.